= EMBED("Forms.ComboBox.1","") error "Reference not valid."

I tried to use Developer > Insert and choose a ComboBox.
In the text field I got = EMBED("Forms.ComboBox.1","")
As I do not know how to use it I started to playing around with the function an edited it. Of course I directly got error messages that what I did was invalid. Problem is that now, I can not take it away, whatever I do I get the Error Message "Reference not valid." It does not matter if I take away the whole function or if I try to set it back to what it was. I don't want to loose everything I did in the workspace!

Thanks, but I cant select anything its all greyed out. I can olny edit that text field, and when I press enter or try to delete it, I get the error message :-(